Numerical Investigation of T-Shaped Microfluidic Oscillator with Viscoelastic Fluid.
Numerical Investigation of T-Shaped Microfluidic Oscillator with Viscoelastic Fluid.
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粘弹性流体T形微流控振荡器的数值研究
DOI：
10.3390/mi12050477
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发表时间：
2021-04-22
期刊：
影响因子：
3.4
通讯作者：
Li F
中科院分区：
文献类型：
--
作者：
Yuan C;Zhang H;Li X;Oishi M;Oshima M;Yao Q;Li F
振荡流在微型器件中有许多应用。目前报道的微流控振荡器的实现方法主要基于撞击射流和康达效应，通常要求流动雷诺数至少为1数量级。另一种方法是在微流控单元中引入弹性膜；但制造工艺相对复杂，长时间运行后膜会变软，导致偏离设计条件。从微流控电路的核心要求即非线性的角度出发，可以通过粘弹性流体流动的非线性特性来实现微流控振荡流动。本文采用二维直接数值模拟（DNS）方法研究了粘弹性流体（boger型）在t形通道及其修正结构中的流动特性。DNS研究的主要结果如下：(1)为了实现周期振荡性能，Weissenberg （Wi）数和黏度比都需要在一定范围内；(2)在上游交叉口附近涡对动态演化存在的情况下，随着交叉口弹性主导面积的增大，振荡强度增大；(3)考虑到t型通道作为潜在振荡器的简单性，改进后的结构应在靠近上壁的入口处雕刻有凹槽。在相同条件下，出口流量标准差测量的最大振荡强度比原标准t型通道提高了129%。综上所述，当Wi数和粘度比在一定范围内时，可以得到oldyd - b型粘弹性流体在标准t型及其修正通道内流动的规律周期振荡特性。该结构具有结构简单、无运动部件、双扇出等优点，在极低雷诺数下可作为极具潜在价值的无源微流控振荡器。
Oscillatory flow has many applications in micro-scaled devices. The methods of realizing microfluidic oscillators reported so far are typically based on the impinging-jet and Coanda effect, which usually require the flow Reynolds number to be at least at the order of unity. Another approach is to introduce elastomeric membrane into the microfluidic units; however, the manufacturing process is relatively complex, and the membrane will become soft after long-time operation, which leads to deviation from the design condition. From the perspective of the core requirement of a microfluidic circuit, i.e., nonlinearity, the oscillatory microfluidic flow can be realized via the nonlinear characteristics of viscoelastic fluid flow. In this paper, the flow characteristics of viscoelastic fluid (Boger-type) in a T-shaped channel and its modified structures are studied by two-dimensional direct numerical simulation (DNS). The main results obtained from the DNS study are as follows: (1) Both Weissenberg (Wi) number and viscosity ratio need to be within a certain range to achieve a periodic oscillating performance; (2) With the presence of the dynamic evolution of the pair of vortices in the upstream near the intersection, the oscillation intensity increases as the elasticity-dominated area in the junction enlarges; (3) Considering the simplicity of the T-type channel as a potential oscillator, the improved structure should have a groove carved toward the entrance near the upper wall. The maximum oscillation intensity measured by the standard deviation of flow rate at outlet is increased by 129% compared with that of the original standard T-shaped channel under the same condition. To sum up, with Wi number and viscosity ratio within a certain range, the regular periodic oscillation characteristics of Oldroyd-B type viscoelastic fluid flow in standard T-shaped and its modified channels can be obtained. This structure can serve as a passive microfluidic oscillator with great potential value at an extremely low Reynolds number, which has the advantages of simplicity, no moving parts and fan-out of two.
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影响因子：
2.7
作者：
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通讯作者：
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DOI：
10.3390/e22010064
发表时间：
2020-01-03
期刊：
Entropy (Basel, Switzerland)
影响因子：
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作者：
Yuan C;Zhang HN;Chen LX;Zhao JL;Li XB;Li FC
通讯作者：
Li FC
影响因子：
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